[GreenKeys] Question regarding TWX and Dial TWX...

[gfmurphy at earthlink.net]

Hi Larry: 

Your RCA machines would have been used to provide Telex service on the
RCA network.  They could not be used for domestic service but could be
used to access machines in other countries.  The dial and the telephone
line connection did not necessarily indicate that it was hooked to a 
voice frequency system such as TWX.  Unless there is a modem , it was
most likely hooked to a neutral circuit.  As others have pointed out, 
the IRCs (International Record Carriers) were allowed to provide telex 
machines in the "Gateway cities."  Since distances were usually not too
great, a neutral circuit was usually adequate.  If I remember correctly,
the gateway cities were: New York, Washington, Miami, New Orleans and San 
Francisco. (Also, whenever the local telco dropped off an outlet for a 
telex or TWX machine, it was always terminated in a 42A connecting block
and the easiest way to connect to one of those was a telephone cord.)

I remember the telegraph office at Standard Oil in San Francisco:  They
had machines from RCA Global Communications, ITT World Communications,
Western Union International, Western Union Domestic and Bell System TWX. 
(There may have been some other carriers that I don't remember.)  There 
were multiple circuits from each carrier.  In addition, they had a private 
line tty circuit to their telegraph office in the UK.  They also had an 
extensive private Teletype network that moved messages to and from their 
facilities in the SF Bay Area.  No Model 32 or 33 equipment there; It was 
all 28 or 35 machines.

Regarding dialing of Telex or TWX numbers:  The use of a dial to establish
a connection seems obvious. That was called Type A dialing.  There was also
Type B dialing where the number keys on the keyboard (and the + character) 
were used to establish the connection.  I remember that ITT World used Type 
B dialing.

According to the FCC, domestic Telex/TWX was anything in North America.
Anywhere else was an international call and had to go through an IRC.

The normal connection in international Telex was a 2 way set-up where the
operators could type back and forth.  In reality, most Telex messages were
of a one way nature (like email).  Where there were big time differences,
all that was really needed was a store and forward setup.  Operators could
send a message to the store-and-forward computer and they would get a
notification back when the message was delivered.  This was cheaper and it
provided a more predictable traffic flow on long haul facilities.  Later
refinements allowed IRC customers to contact the store-and-forward computer via
dial-up terminals (remember computer time share terminals?) to send or pick 
up messages from locations outside of gateway cities.  When dial-up terminals
were available, you did not need a Telex machine or line.  All that you had
to have was a Telex number from one of the IRCs and a password.  Protocol and
speed conversion from the dial-up terminals were provided by the store and
forward computer.  But, in the end, FAX machines and email did in the Telex
system.

A circuit for interfacing a 5 level machine to a Telex line is described in
in the M32 manual (309B - Vol 1).  For those of you who have Telex machines,
it describes what is happening on the line.  You can build the "office end"
of the circuit and get your machine to turn on and off by reversing the line
polarity.

Regards, Jerry Murphy




-----Original Message-----
>From: Larry Tighe <larryradio at att.net>
>Sent: Apr 23, 2010 12:12 PM
>To: Jim Haynes <jhhaynes at earthlink.net>
>Cc: greenkeys at mailman.qth.net, Bryan Brodie <b.brodie at vaporland.com>
>Subject: Re: [GreenKeys] Question regarding TWX and Dial TWX...
>
>Thanks Jim and Don,
>
>BUT, where do my RCA Global Model 15's fit into all this?  They have rotary 
>dials on the accompanying box and a telephone line connection...2 wire.
>
>Did RCA Global have the international business? Or, did they compete with 
>W.U.?  I think my RCA Model 15's deserve recognition in this discussion  LOL
>
>lar